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D.E. Nix, K.R. Matthias, R.W. Snyder; Fungal Survival in Fourth–Generation Fluoroquinolone (FQ) Ophthalmic Preparations . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4885.
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Purpose: Newer generation topical FQ’s are being increasing used in patients undergoing ophthalmic surgery. Bacterial contamination risk is minimal considering the broad spectrum activity of FQ’s and high concentrations present; however, these preparations may be susceptible to fungal contamination. The survival of Candida albicans, Candida parapsilosis and Aspergillus niger were evaluated in commercial preparations of 0.3% gatifloxacin (Zymar) and 0.5% moxifloxacin (Vigamox). Methods: Original bottles of gatifloxacin and moxifloxacin were inoculated with approximately 10^6 colony forming units of the three fungal isolates using procedures consistent with USP procedures for preservative effectiveness testing. The solutions were removed and also tested in glass tubes to evaluate if the container had any effect. Colony counts were determined at baseline, 4, 24, 48, 96, and 168 hours to determine fungal survival. Results: For Candida isolates, a 2.2 to 2.4 log decrease in organism density was seen in the first 4 h with gatifloxacin solution in glass tubes compared to 0.2 to 0.8 log decrease with moxifloxacin solution. A relatively steep loss of viable yeast was noted over 4 h with gatifloxacin and over 24 h with moxifloxacin, then the decline continued but at a slower rate for both drugs. At 7 days, concentrations of C. albicans in gatifloxacin solution were below the quantifiable level and only a few colonies were observed. A mean of 620 colonies/ml were present in the moxifloxacin solution. For C. parapsilosis, 120 colonies/ml in gatifloxacin solution and 8000 colonies/ml in moxifloxacin solution remained at 7 days. The A. niger density decreased almost 2 logs in the gatifloxacin solution and 0.25 log in the moxifloxacin solution at 4 hours; however, fungal counts were similar for both solutions from 24 h to 7 days. Similar results were observed for both drugs in the original bottles but counts were slightly higher (0.1 to 1.5 log) at all time points. The gatifloxacin formulation contains 0.005% benzalkonium chloride as a preservative and EDTA with pH adjusted to 6.0. In contrast, the moxifloxicin formulation does not contain a preservative, the pH is adjusted to 6.8 and an unspecified concentration of boric acid is present. Conclusions: Neither formulation supported the growth of Candida sp. or A. niger; however, the gatifloxacin formulation reduced fungal counts more rapidly and to a greater extent than the moxifloxacin formulation.
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